This invention relates to separating apparatus, and more particularly to an air stream separator, for example for separating chips or biomass from heavier material.
In air stream separation, the material to be separated is introduced in mixed condition into an air stream, whereby the material is divided into fractions, of which the lightest material follows along furthest in the air stream direction. In the initial phase of separation, i.e. when the material is being introduced into the separating air stream, the material behaves in unsorted manner, and after having been passed through a certain distance, a heavier fraction, for example, has been separated from other fractions. The distance, through which the material is unsorted, can be relatively long. This is a disadvantage, because the air stream separating installation must be designed with greater dimensions.
When the starting material, from which, for example, stones and metal particles are to be separated, consists of a lot of particles having about the same size and density, heavy particles can be separated by air stream separation and by using known art, without affecting the particle distribution of the material.
When, however, the light phase consists of a mixture of particles having varying density and/or size, air stream separation carried out according to known art results in the light phase being separated in such a manner that particles with similar properties are gathered together. A starting material in which particles with different properties are well mixed, thereby is converted into a material partially classified with respect to size and/or density. In many industrial processes it is desirable that the material be well mixed. Air stream separation according to known art, therefore, produces the disadvantage, that chips, from which, for example, stones have been removed after the separation are divided into fractions of similar fragment size.
It is also desirable to separate stones and other heavy impurities from biomass, which itself includes heavy fractions, such as stump parts, branch parts etc.